the poll has 2 people who lost contrast after 1 year and 1 person who lost contrast after 2 years.

Which doesn't really prove anything (you believe website polls are scientifically accurate?). For all we know those could be cases of faulty hardware, subjective mis-impressions on their parts as to the contrast changing, or people just making up responses to the poll.

I have never heard of any technical information that says eInk screens have a finite lifespan with regards to fading/contrast. If you know otherwise, please provide links.

Which doesn't really prove anything (you believe website polls are scientifically accurate?). For all we know those could be cases of faulty hardware, subjective mis-impressions on their parts as to the contrast changing, or people just making up responses to the poll.

Faulty hardware or mis-impressions are just as valid for the original poster, who is trying to determine the likleyhood of him experiencing the same issue, whatever the reason.

I agree, it's rare, and doesn't seem to be a systematic problem. However, I am cognizant of the fact that such a problem could become more likely in later years, so I think it's too soon to draw any strong conclusions about the lifetime contrast of such screens.

Faulty hardware is a completely different problem, which has nothing to do with the (incorrect) notion that all eInk has an inherent finite lifespan because of contrast fading. The later simply does not exist.

I suspect that when the original poster said "I've read some comments saying that e-ink screens lose contrast over time and thus have relatively short lifespans."... what he's referring to are comments about the initial fading that occurs with brand new devices (which stops after the first few weeks), and misinterpreted those comments.

The 1st generation eink screen did fade after some time. But after that fade, it didn't fade any more then that. The Vizplex screen in my 505 has not faded in longer then it took the 500 to fade. So take that as you will.